Guys, take a look at this 485 waveform. Why is there a period of time in the middle, and then it causes my reception to go wrong?

史上最萌反派

Guys, take a look at this 485 waveform. Why is there a period of time in the middle, and then it causes my reception to go wrong? [Copy link]

 

The ideal waveform should not have this middle section...

The first picture takes too long to use 6.2us

The second picture has a shorter time and can be 2.4us

maychang

I have never seen a 485 waveform with a dead zone.

What did you use to generate the 485 signal?

Receiving errors are not necessarily caused by "a period of time in between", but may also be caused by other reasons.

fxyc87

485 needs to use twisted pair cable, and terminal resistors need to be added. If that doesn't work, add shielded wire.

fxyc87

Oscilloscope is good.

dcexpert

You need to look at your 485 design and wiring, and analyze how the intermediate levels are generated.

btty038

You connected the wires incorrectly. I have encountered this situation before. Check your output terminals.

chunyang

The generation of intermediate levels is either due to a circuit error, such as excessive bias, or a level competition between terminals, in which case it is a software problem.

史上最萌反派

maychang posted on 2022-12-15 13:56 I have never seen a 485 waveform with a dead zone. What did the OP use to generate the 485 signal? Receiving errors are not necessarily caused by "there will be a period of time in the middle...

Thanks for your reply, it has been solved. Because the broadcast address is used, the middle one becomes two frames of data superimposed

史上最萌反派

btty038 posted on 2022-12-16 04:32 You connected the wires incorrectly and did not connect them. I have also encountered this situation. Check your output terminal

Thanks for your reply, it has been solved. Because the broadcast address is used, the middle one becomes two frames of data superimposed

史上最萌反派

chunyang posted on 2022-12-16 17:28 The intermediate level is either caused by a circuit error, such as excessive bias, or a level competition between terminals. In this case, it is a software problem.

Thanks for your reply. It was caused by using the broadcast address. Changing the address made it successful. There is no intermediate level.

史上最萌反派

fxyc87 posted on 2022-12-15 17:04 The oscilloscope is good.

Hahaha, the company's

史上最萌反派

btty038 posted on 2022-12-16 04:32 You connected the wires incorrectly and did not connect them. I have also encountered this situation. Check your output terminal

The line is not connected correctly, the 485 address is wrong, the broadcast address is used

chunyang

The cutest villain in history was published on 2022-12-21 11:08 Thank you for your reply. It was caused by the use of the broadcast address. It was successful after the address was changed. There is no intermediate level.

The broadcast address is not the cause of the problem, but the process and/or timing of initiating the broadcast is incorrect, resulting in level competition.

Gen_X

Will the broadcasts overlap?

It must be the imperfect protocol processing that leads to the above conflict problem!

shuangchafeng

Receiving errors are not necessarily caused by "a period of time in between", but may also be caused by other reasons.

tomas_li

The host sends a broadcast address to multiple slaves on the 485 bus. After receiving the broadcast address, the slaves will reply data to the bus, resulting in the superposition of levels on the bus. For example, a positive level is superimposed with a negative level to become an intermediate level. Dear experts, is my understanding correct? The host measured the receiving level of the host, so the waveform of the intermediate level was observed.

史上最萌反派

tomas_li posted on 2023-2-17 09:53 The host sends a broadcast address to multiple slaves on the 485 bus. After receiving the broadcast address, the slaves will reply data to the bus, resulting in the superposition of the bus level...

That’s how I understand it.